1. Field of the Invention
The invention relates to a pneumatic or hydraulic actuation device comprising a cylinder with a piston which is slideably guided in the cylinder and, for transmitting actuation movements, is provided with at least one piston rod that sealingly extends out of the cylinder, through a cylinder cover and is connected to a securing disc.
2. Description of the Prior Art
In known actuation devices of this type the securing discs, which are used to connect the actuation cylinder to the machine parts driven by the latter, are screwed on the ends of the piston rods. The piston rods are either provided with an outer thread, onto which a nut is screwed, or they have a threaded bore originating at their front end. In both cases, the securing disc is clamped rigidly against the front end or against a collar of the piston rod. This is a simple and reliable connection of machine parts. In practice, however, it has been shown that the screws on the securing disc become detached relatively easily and that, in constructions with a plurality of parallel piston rods, the latter may become trapped when extending and their guides are subjected to unexpectedly high stresses.
The object of the invention is to improve upon the known actuation devices of the initially-mentioned type of construction, in particular the construction with two or more parallel piston rods, in such a way that the connection of the securing disc to the ends of the piston rods cannot become loose unintentionally, nor does twisting of the piston rods with resultant over-stressing of the guides occur.